What are the relationships between comets and meteors?

If the shower meteors come from comets, isn't it likely that the meteorites come from comets too?What are the relationships between comets and meteors?
Comets





Comet. Image courtesy of NASA.





Many comets exist. Approximately 12 are discovered each year, mainly by amateurs. Several hundred billion are estimated to exist.





Comets have very elliptical (elongated, not round) orbits. It takes comets varying lengths of time to orbit the sun. Some have fairly short periodicities (3 years) and others have periodicities of hundreds of thousands of years. For example, Halley's comet returns every 76 years. It was first seen in 240 BC by the Chinese.





Millions of comets are believed to form a roughly spherical cloud (called the oort cloud) beyond the orbit of Pluto, at a distance of about 100,000 AU, nearly half the distance to the nearest star. (Pluto's orbit is at about 40 AU, varying from 29.7 to 49.2 AU.)


Comets tend to be small (several km in diameter). For example Halley's comet is 16 x 8 km.





Essentially large dirty snowballs, composed of a porous mixture of frozen gases, rocky and metallic material:





water ice (Halley's comet is 80% water)


carbon dioxide (dry ice)


ammonia


methane


Note: You can make a comet in the classroom with dry ice, ammonia, dirt, etc.





As a comet nears the sun, solar energy vaporizes frozen gases, forming a glowing ';head'; called a coma.





The comet also develops a tail of ionized gases and dust that may be millions of km long. The tail always points away from the sun, (due to radiation pressure and solar wind) and only follows behind the comet as the comet approaches the sun. As the comet moves away from the sun, the tail preceeds the head.





Comets have no light of their own, but reflect sunlight.


Meteor showers are associated with comets. They occur when the Earth passes through the debris of a (burned out) comet.





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Meteors, meteoroids, and meteorites


Meteor = shooting star.


Glow of small particles being heated as they enter the atmosphere.


Can see 6 - 60 per hour.


Meteorites = rocks that reach the earth's surface from space.





Meteoroid = the object before it enters the Earth's atmosphere. Most are destroyed by about 80 km above the earth's surface.





Fireballs = very bright meteors with trains that last up to 30 minutes.





Bolide = Fireball that breaks up on atmospheric entry.


Possible source of CO2?What are the relationships between comets and meteors?
Asteroids





When we talk about asteroids, we talk about objects whose range in diameters goes from ~10m to 963 km (1 Ceres). Most of these objects are on orbits that are stable for long periods of time (1 billion year or more). However, some of them may happen to be displaced, for several reasons, to special orbits that are ';in resonance'; with the orbit of Jupiter (or Saturn). When we say that an asteroid is in resonance we mean that its period is a simple fraction of the period of Jupiter. So, for example, if an asteroid revolves around the Sun with a period which is 2 times that of Jupiter, we say that it is in a 2:1 resonance with Jupiter. This is important because Jupiter is gravitationally perturbing the asteroid's orbit. If there is no special relationship between the two orbital periods, the perturbations pull the asteroid's orbit in different directions, and the net effect is null over a single orbit. But if there is a special relationship between the planet and asteroid period, the perturbations may have an average that is not null over an asteroid orbit, and the net effect is that the asteroid orbit is ';distorted';.





The orbit of the asteroid, which is an ellipse, may become more elliptical, and if the perturbations are strong enough, the asteroid may go in an orbit that is going to put it in a collision path with the Sun. That is how asteroids disappear.





Comets





Most of the brightest comets are object that are either on very eccentric orbits (elliptical orbits in which one of the axis is much longer than the other) or on unbound orbits (orbits that are not closed, they can be parabolyc or hyperbolic). What happens with these comets is that either they pass once close to the Sun, when they became active and therefore visible, with a next passage that is going to happen hundreds of thousand of years afterwards (comets on highly eccentric elliptical orbits), or either they pass close to the Sun once, and then never again (parabolic or hyperbolic comets). In this sense comets ';disappear';. Another way in which comets may disappear is by crushing into the Sun. There are at list ~30 comets per year that have this destiny: we call these objects ';Sungrazers';.
Asteroids and comets are both classified as near-Earth objects. Asteroids are made of rock or metal and are thought to have been created in the warmer inner solar system. Comets are composed of ice, rock, and organic (carbon-based) compounds, and are believed to have formed in the cold outer solar sytem. Scientists believe both are ';...ancient remnants of the earliest years of the formation of our solar system more than four billion years ago.';
From my understanding a comet my bring meteor showers because debris in space collects at the tail of the comet. So when the comet gets close enough to Earth it showers some of that debris known as meteor showers on the Earth. The meteors however are not exclusive to comets. They are rogue fragments of mineral an rock from planets drifting though space.